Astronauts experience ‘space anemia’ when they leave Earth

When we are on Earth, our bodies create and destroy two million cells per second. A new study shows that astronauts witnessed 3 million red blood cells destroyed in space per second, resulting in 54% more cell loss than people experience on Earth.

A low red blood cell count in astronauts is known as anemia in space.

Study author Dr. Jay Trudel, MD, a rehabilitation physician and researcher at The Ottawa Hospital and Professor at the University of Ottawa, said in a statement.

The researchers took breath and blood samples from 14 astronauts before their six-month stay on the International Space Station. The astronauts also took samples four times during their flights. The researchers also collected blood from astronauts for up to a year after their spaceflights.

The trips of 11 men and three women occurred between 2015 and 2020. The results were published Friday in the journal Nature Medicine.


When astronauts are in space, they experience a shift in body fluids toward the upper body due to a lack of gravity. This leads to increased pressure on the brain and eyes, causing Cardiovascular problems and a loss of 10% of fluid in the blood vessels.

A special sleeping bag can help astronauts with vision problems in space

Researchers believe that space anemia was the body’s way of adapting to shifting fluids, destroying red blood cells to restore balance. They also believed that the loss of red blood cells was only temporary, as it recovered itself after astronauts adjusted after spending 10 days in the space environment.

Trudel and his team discovered a surprising result – the space environment is the actual culprit.

“Our study shows that upon reaching space, more red blood cells are destroyed, and this continues for the duration of the astronaut’s mission,” he said.

European Space Agency astronaut Tim Peake appears after completing his first blood draw in space.

The research team has developed methods for measuring red blood cell destruction, including measuring the amounts of carbon monoxide detected in breath samples taken from astronauts. Each time one molecule of heme, or the characteristic red pigment in red blood cells, is destroyed, it produces a molecule of carbon monoxide.

The team was unable to directly measure the astronauts’ red blood cell production, but they speculate that the astronauts may have experienced the generation of additional red blood cells in response to the increased destruction. If this had not happened, all the astronauts would have experienced the effects and health problems associated with severe anemia while in space.

“Fortunately, having fewer red blood cells in space is not a problem when your body is weightless,” Trudel said. “But when landing on Earth and possibly on other planets or moons, anemia affecting your energy, stamina, and strength can threaten mission goals. You don’t feel the effects of anemia until you land, and you have to deal with gravity again.”

long term effects

After returning to Earth, five of the thirteen astronauts were diagnosed with clinical anaemia. One astronaut did not draw his blood after landing.

Treatment of the first known blood clot in space

Follow-up samples from the astronauts showed that anemia in space was reversible because their red blood cell count gradually returned to normal between three and four months after their return.

However, samples collected a year after the astronauts landed on Earth showed that the rate of red blood cell destruction was still increasing, about 30% higher than what they experienced before their spaceflights.

The researchers believe this indicates that long-duration spaceflights can lead to structural changes affecting red blood cells.

The findings are the first published results from the MARROW Experiment examining bone marrow health and blood production when astronauts are in space.
NASA astronaut Anne McClain is shown carrying vital medical equipment for MARROW on the International Space Station.
The findings highlight the importance of screening both astronauts and space tourists for health conditions that could be affected by anemia and monitoring for any problems during missions. A previous study by Trudel and his team also revealed that longer spaceflights exacerbate anemia.

Currently, it is uncertain how long the human body can support the increased rate of red blood cell destruction and production.

In order to combat this risk, researchers suggest changing the astronauts’ diet to support better blood health.

Lessons learned from this research can also be applied to anemic patients on the ground, especially those who suffer from it after illness and prolonged bed rest. While the direct cause of this type of anemia is unknown, it may be similar to what occurs in space.

“If we can figure out exactly what’s causing this anemia, there is potential to treat or prevent it, both for astronauts and for patients here on Earth,” Trudel said. “This is the best description we have of controlling red blood cells in space and after returning to Earth. We were surprised and rewarded for our curiosity.”


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